Suppose $$X=\{1,2,3 \}$$ $$C=\{\{1\},\{2\},\{1,3\}\}$$ $$U=\{\{2\},\{1,3\}\}$$ Can I say that $C$ is a cover of $X$ and $U$ is a subcover of $C$? If not,why?

Is there a test which reliably decides whether two Bezier curves intersect or not? I don't need to know how many intersections there are or at what p...

So far I've reasoned that $\mathbf{a}$ and $\mathbf{b}$ can't be both negative, because $\sqrt{21-12\sqrt{3}}$ cannot be negative. Also $\mathbf...

I'm preparing for an exam and was solving a few sample questions when I got this question - Factorize : $$(x+1)(x+2)(x+3)(x+6)- 3x^2$$ I don't r...

They meet the requirements of both having an $=$ number of vertices ($7$). They both have the same number of edges ($9$). They both have $3$ vertices of d...

can someone show me how to differentiate stuff like x + 2 and I've never did this before and I use the most god awful textbook imaginable. Much thanks

Sketch the following regions: $\operatorname{Arg}(e^z)>\dfrac{π}{4}$ ${e^z|\operatorname{Im}(z) = 1}$ $|e^z| > 2$ I am confused of graphing $e^z$ fu...

$\newcommand{\lcm}{\operatorname{lcm}}$ Let $m,n$ $\in$ $\Bbb N$. The least common multiple ($\lcm$) of $m,n$ is the smallest natural number $x$, such tha...

I have the next question: Let $K \subset $ $R^1$ consist of $0$ and the numbers 1/$n$, for $n=1,2,3,\ldots$ Prove that $K$ is compact directly from the de...

Could you give me an example of function $ f \colon \mathbb N \to \mathbb Z$ that is both one-to-one and onto? Does this work: $f(n) := n \times (-1)^n$? ...